aya/aya-log/README.md

# aya-log - a logging library for eBPF programs

## Overview

`aya-log` is a logging library for eBPF programs written using [aya]. Think of
it as the [log] crate for eBPF.

## Installation

### User space

Add `aya-log` to `Cargo.toml`:

```toml
[dependencies]
aya-log = { git = "https://github.com/aya-rs/aya-log", branch = "main" }
```

### eBPF side

Add `aya-log-ebpf` to `Cargo.toml`:

```toml
[dependencies]
aya-log-ebpf = { git = "https://github.com/aya-rs/aya-log", branch = "main" }
```

## Example

Here's an example that uses `aya-log` in conjunction with the [simplelog] crate
to log eBPF messages to the terminal.

### User space code

```rust
use simplelog::{ColorChoice, ConfigBuilder, LevelFilter, TermLogger, TerminalMode};
use aya_log::BpfLogger;

TermLogger::init(
    LevelFilter::Debug,
    ConfigBuilder::new()
        .set_target_level(LevelFilter::Error)
        .set_location_level(LevelFilter::Error)
        .build(),
    TerminalMode::Mixed,
    ColorChoice::Auto,
)
.unwrap();

// Will log using the default logger, which is TermLogger in this case
BpfLogger::init(&mut bpf).unwrap();
```

### eBPF code

```rust
use aya_log_ebpf::info;

fn try_xdp_firewall(ctx: XdpContext) -> Result<u32, ()> {
    if let Some(port) = tcp_dest_port(&ctx)? {
        if block_port(port) {
            info!(&ctx, "❌ blocked incoming connection on port: {}", port);
            return Ok(XDP_DROP);
        }
    }

    Ok(XDP_PASS)
}
```

[aya]: https://github.com/aya-rs/aya
[log]: https://docs.rs/log
[simplelog]: https://docs.rs/simplelog